UV-transmission fabric, method of obtaining the same and garment being made of the said fabric

ABSTRACT

A fabric includes a first yarn having a UV-A transmission of between 10 and 50% while substantially blocking UV-B transmission, and at least a second yarn different from the first yarn, the yarns being interweaved such that the fabric has regular mesh openings that give rise to a transmission of the fabric of between 20 and 65% for UV-A and between 3 and 20% for UV-B.

BACKGROUND OF THE INVENTION

The invention pertains to a UV transmissive fabric that has atransmission of between 20 and 65% for UV-A and between 3 and 20% forUV-B. The invention also pertains to a method of manufacturing such afabric and a garment being made by using the fabric.

EP-0 267 655 B1 discloses a UV-filter of the type indicated above, whichmay be in the form a warp-knitted fabric of polyester fibres and issuitable for protecting human skin from the damaging effects ofexcessive exposure to solar radiation while permitting immediate pigmenttanning and encouraging the de-novo melanin synthesis. To this end, theknown filter is essentially transmissive to ultra violet radiation inthe UV-A range (320-400 nm), while it is essentially opaque forultraviolet radiation in the UV-B range (290-320 nm). However, a certainleakage of UV-B radiation is said to be desirable for stimulating themelanocytes to produce greater quantities of new Melanin, which willthen be available for tanning by UV-A.

Although the known fabric is suitable for constituting e.g. a screenthat allows people to get tanned while decreasing the risk of severesunburn, this fabric is limited in applicability given its specificmechanical and colouring properties. It is for example not suitable formaking comfortable and appealing outerwear.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a fabric that hasadequate UV-transmission characteristics to enable skin tanning andstill have a relatively high sun (or solar) protection factor (commonlyknown as SPF), which fabric is less limited in applicability.

To this end a fabric has been provided comprising a first yarn having aUV-A transmission of between 10 and 50% while substantially blockingUV-B transmission, and at least a second yarn different from the firstyarn, the yarns being interweaved such that the fabric has regular meshopenings that give rise to the required transmission characteristics.

The invention started off with the recognition that in the prior artfabric, the yarn used must provide all relevant properties to thefabric, i.e. the UV-transmission properties as well as the mechanicalproperties and the susceptibility to dyes. Since the UV-transmissioncharacteristics are essential for the fabric, the other properties areoften a mere outcome, or at least there is a very limited freedom inchoice for these properties. Based on that recognition, applicantrealised that the freedom of choice could be greatly enhanced when theproperties of the fabric can be controlled more independently from eachother. This lead to the first feature of the invention, namely taking ayarn that meets restricted UV transmission characteristics, i.e. between10 and 50% for UVA while substantially blocking (either by absorption orreflection or a combination of both) UV-B transmission. Blocking in thesense of this invention means a transmission of up to approximately 5%for UVB. A typical transmission for a suitable yarn is between 0 and 3%for the UVB between 290 and 310 nm (which is the most harmful part ofthe UVB radiation). At first sight this substantial UVB blocking mightseem contradictory to the necessary transmission properties of theultimate fabric. However, it was applicants merit to realise that anadequate transmission of the fabric for UVA (between 20 and 65%) and UVB(between 3 and 20%) can still be provided by taking a second yarn, andinterweaving (for example by weaving or knitting) both yarns such thatregular mesh openings arise for obtaining the proper UV transmission ofthe fabric. Given the fact that the UV transmission properties of thefirst yarn are quite strict, the UV transmission properties of thesecond yarn do not have to meet stringent demands. Most materials formaking yarns, either synthetic or natural, essentially block UVA as wellas UVB. However, by using at least this second yarn for making thefabric, even if this yarn totally blocks UV radiation, thetransmissiveness of the fabric can be increased (instead of limited)when compared to the transmissiveness of the first yarn, simply byproviding the regular mesh openings. On the other side, if for example asecond yarn would be used that has a very high transmissiveness for UVA(e.g. over 60%) and UVB (e.g. over 20%), adequate transmissiveness forthe fabric can still be obtained by applying an adequate (not too high)amount of the second yarn and relatively small mesh openings.

The application of at least one other yarn next to the first yarn meansthat the ultimate properties of the fabric are determined also by theproperties of the second yarn. Moreover, by starting off with a firstyarn with the very restricted UV transmission properties as indicatedhere-above, there is a great freedom in choice for the second yarn, thusenabling the skilled practitioner to provide an extended range ofproperties, in particular mechanical and colouring properties, for theultimate fabric. Moreover, since the UV-transmission properties can becontrolled more precisely, it has been found that favourable UV-Atransmission properties of between 25 and 60% and between 5 and 15% forUV-B can be provided for the fabric. In particular, when applying thepresent invention a fabric can be provided having a UV-A transmissionbetween 30 and 45% and a UV-B transmission between 10 and 12%. Thelatter fabric has an SPF of about 8 while still providing very good skintanning. Such properties can be advantageously provided preferably witha first yarn having an UV-A transmission of between 20 and 50%, mostpreferably about 30%.

In an embodiment the second yarn is a non-elastic yarn. Non-elastic inthe sense of this patent means that the yarn cannot be reversiblyelongated more than 5% in length. This embodiment can lead to a fabricthat is very suitable for loosely worn outerwear such as shirts, shorts,skirts, dresses etc. In a further embodiment, the first and second yarnsare interweaved via a double-knitting process. The double knitted fabricor double Jersey having a certain amount of e.g. natural non-elasticyarn such as cotton, is favourable for use as a garment, especially forouterwear, in terms of its improved strength, grip, texture andappearance and in terms of its heat insulation and wind protectionproperties and its ability to absorb human sweat. The inventor has foundthat it is possible to configure such a double Jersey so as to fulfilthe UV transmission requirements, in spite of the relatively closebonding structure and the presence of second yarn which is essentiallynon-transparent to both UV-A and UV-B. In an embodiment the content ofthe non-elastic yarn is between 15 and 85%, preferably between 50 and60%, based on the total weight of the fabric. This way a very broadrange of mechanical and colouring properties is provided while stillbeing able to meet the UV-transmission properties by providing anadequate regular mesh structure. Preferably the weight of the fabric isbetween 90 and 180 g/m², more preferably between 125 and 150 g/m². Inparticular at a weight of approximately 130 g/m2, a non- or hardlytransparent fabric (i.e. with respect to visible light) can be providedthat still meets the UV-transmission demands (for example bydeliberately dropping stitches in the double-knitting process).

In an alternative embodiment the second yarn is an elastic yarn. In thisembodiment a fabric is provided that is typically worn while beingstretched to a certain amount, typically up to 15%, such as swim- andbikewear. In an embodiment the second yarn is a naked yarn (i.e. notcovered with another yarn), typically giving rise to a more or lesscoil-like fibre structure, and the content of the second yarn is between10 and 30%, preferably around 20%, based on the total weight of thefabric. When the content of the second yarn is more than 30% it appearsthat the UV-transmission demand cannot be reasonably met. In particular,the transmission factors will generally be too low. By applying acontent less than 30%, preferably around 20%, a fabric can be providedthat is very suitable for outerwear that is typically worn under stretchconditions. In an embodiment the fabric contains 30-50% of the firstyarn, and up to 60% of a third yarn, the third yarn being non-elastic.

In another embodiment that the second yarn is an elastic corespun yarn.A corespun yarn is a yarn wherein the core is covered with a second yarn(see also ASTM Method D123). Such yarns are commonly known and forexample described in U.S. Pat. No. 5,303,550. It appears that by using acorespun yarn, smaller and/or fewer meshes can be used while still beingable to obtain sufficient UV-A and UV-B transmissiveness. This isadvantageous e.g. because higher weights of the fabric can be used. Sucha fabric can be less transparent for visible light (also depending onthe colour of the dyestuff) which for many applications is moreappealing to wearers. It even appears that fabrics which are worn undervery low stretch conditions can still have sufficient UVtransmissiveness features despite the fact that they are hardlystretched out. It appears that a fabric according to this embodiment isvery suitable for outerwear that is worn under low stretch conditions,typically up to 8%, such as tops, dresses and t-shirts. In an embodimentthe fabric contains up to 30% of the second yarn based on the weight ofthe fabric. This appears to give rise to a fabric which is verycomfortable for making outerwear. Preferably the fabric contains up to10%, based on the weight of the fabric, of the second yarn.

The invention also pertains to a method for manufacturing a fabriccomprising taking a first yarn having a UV-A transmission of between 10and 50% while substantially blocking UV-B transmission, taking at leasta second yarn different from the first yarn, and interweaving the yarnssuch that the fabric is provided with regular mesh openings that giverise to a transmission of the fabric of between 20 and 65% for UV-A andbetween 3 and 20% for UV-B. Preferably, the yarns are interweaved via aknitting process.

The invention will be further explained by using the following examplesand figures. All percentages are weight percentages unless indicatedotherwise.

Example 1 describes a method for measuring the UV transmissiveness ofyarns and fabrics

Example 2 discloses yarns for use in a fabric according to the invention

Example 3 discloses fabrics according to the invention and methods formanufacturing these fabrics

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged schematic view of a circular double knitted fabricaccording to the invention

FIG. 2 is a schematic view of a circular knitting machine

FIG. 3 is a flow diagram illustrating a manufacturing process of afabric.

DETAILED DESCRIPTION Example 1

Measurement of UV transmission (i.e. energy intensity of UV radiationpassing through versus energy intensity of incident radiation) of yarnsand fabrics can be done using a spectrophotometric analyser. Suchmeasurements have for example been described in the research disclosurecalled “Examination of the absorption properties of various fibres inrelation to UV radiation”, by Joanna Alvarez c.s., as published in AUTEXResearch Journal, Vol. 3, No 2, June 2003. In the paragraph called “UVspectrophotometric method of measuring the UV penetration index” amethod for determining UV transmissiveness is described using a DK-2Aspectrophotometer from Beckman. The fabrics are measured as such, theyarns are measured by making a so called “Hollander Weave” of the pureyarn and measuring the resulting fabric. The Hollander Weave is type ofplain weave, in this case with the warp wires of the same diameter thanthe weft wires. The weave is very dense with virtually no apertures,therefore, the yarns as such account for the UV radiation transmitted.

The UV transmission of the yarn is not only determined by theconstituting material, e.g. the type of polyester, polyamide,polyethylene etc. but to an important extent also by parameters such asthe thickness of the yarns, the number of filaments, the smoothness ofthe yarns (resulting in yarns ranging from “bright” to “dull”), theshape of the cross-section of the yarn (for example circular, hexagonal,square etc.) and optional additives such as brighteners added to thematerial of the filaments. Each of these parameters has an effect on theUV transmission. By varying these features an optimum result can befound for each application of a particular yarn to produce a particularfabric. With respect to a fabric made by interweaving various yarns, theUV transmissiveness not only depends on the type of yarns used but alsoon the method of interweaving, the applied dyestuff, optional additivessuch as softeners etc.

Example 2

Since the UV transmissive properties of the yarns, as outlinedhere-above, depend on many parameters and interdependencies of theseparameters, the properties of suitable yarn cannot be specified simplyby giving exact ranges for these parameters. This would unduly restrictthe scope of the invention. Therefore, the yarns for use according tothe invention are specified by the required UV transmissiveness.Relevant yarn parameters (such as material, thickness, number offilaments etc) that may influence this UV transmissiveness are disclosedunder example 1, and the result of changes for these parameters can bedirectly and positively verified by the UV-transmission test asdescribed here-above. With respect to a fabric made by using theseyarns, the UV transmissiveness not only depends on the type of yarnsused but also on the method of interweaving, the applied dyestuff, theoptional use of additives etc. Therefore, with respect to the UVtransmissiveness of the fabric, it is clear that this is specified alsoby stating the required UV transmission values.

Yarns that are transmissive for UV-A and block UV-B as specified in theappended claims are the polyester yarn type 55f20 t1001 (55Dtex, 20filaments, bright, circular cross-section) available from KordsaInternational Wilmington, Del., USA (formerly DuPont Sabanci Polyester);type 50f22 polyester yarn (55Dtex, 22 filaments, bright, circular crosssection) available from Setila S.A., Valence, France; type 50f20 t625Spolyester yarn (50Dtex, 20 filaments, bright, circular cross section)available from Trevira, Hattersheim, Germany and type 50f18 polyesteryarn (50 Dtex, 18 filaments, bright, circular cross-section) availablefrom Brilén, Barbastro, Spain.

Non-elastic yarns for use in the fabric according to the invention arei.a. cotton, e.g. 70/1 NM, viscose, hemp, flax etc.

Elastic yarns for use in the fabric according to the invention are i.a.elasthane yarns such as LYCRA, elastic fibre available from Invista,Whichita, USA; Dorlastan, elastic fibre available from Asahi KaseiSpandex Europe GmbH, Frankfurt, Germany and Dow XLA elastic fiber,available from Dow Fiber Solutions, United Kingdom. Other suitable yarnsare Elastic Polyester available from Trevira GmbH Werk Guben, Guben,Germany and Elastic Polyester available from Weber & Heusser, Albstadt,Germany.

Corespun yarns are available i.a. from Weber & Heusser, Albstadt,Germany and Fein-Elast Umwindewerk GmbH, Lustenau, Austria. A firstexample is a yarn based on Dorlastan (44Dtex; 8.34 weight %) and coveredwith 70/1 NM combed cotton (91.66 weight %). A second example of acorespun yarn is based on LYCRA (44Dtex) and covered with polyester50f24 (50Dtex, 24 filaments). A third example is based on Dow XLAelastic fiber (44Dtex) and covered with 50/1 NM combed cotton. A fourthexample is Dorlastan (44Dtex) covered with polyester 50f24 (50Dtex, 24filaments).

Example 3

A fabric according to the invention can be made according to anysuitable interweaving method, as long as meshes are provided that leadto the UV transmission rates as specified in the appended claims.Methods usable in the present invention are for example described in“Knitting Technology: A Comprehensive Handbook and Practical Guide toModern Day Principles and Practices” by David J. Spencer (1989). Othersources of suitable methods are for example “Wellington Sears Handbookof Industrial Textiles” by Sabit Adanur (1995) and “Handbook of Weaving”of the same author (2001).

Common types of interweaving which appear to be suitable for obtaining afabric according to the invention are the commonly applied “weft knit”,e.g. a double-knitting method (also called “double Jersey”) which istypically used for circular knitting, and a “warp knit” which istypically used for flat knitting. With these types of interweaving fivetypes of fabric which fulfil the UV transmission demands of the presentinvention have been made. Fabrics 1, 3 and 4 have been made as a weftknit, in particular a double Jersey knit. Fabrics 2 and 5 have been madeas a warp knit.

-   Fabrics 1, 1′: 55% combed cotton 70/1 NM; 40% 55f20 t1001 polyester    yarn; 5% Corespun Dorlastan (1) or Corespun Lycra (1′) as described    under example 2.-   Fabric 2: 80% 50f22 polyester yarn; 20% LYCRA (44Dtex, bright, type    269B)-   Fabric 3: 55% uncombed cotton 70/1 NM; 45% 55f20 t1001 polyester    yarn-   Fabric 4: 48% combed cotton 50/1 NM; 45% polyester (50f20 of Setila    S.A.); 7% Corespun XLA Dtex 44 as described under example 2-   Fabric 5: 78% 55f20 polyester yarn; 22% Dow XLA Dtex 44

Fabrics 1, 1′ and 4 appear to be very suitable for women's tops, dressesand T-shirts (little stretch). Fabrics 2 and 5 appear to be verysuitable for swim- and bikewear (significant stretch). Fabric 3 appearsto be suitable for all kinds of regular shirts, e.g. polo shirts(typically no stretch).

FIG. 1

As is shown in FIG. 1, a pique-type double knitted fabric 10 accordingto the invention is composed of transparent natural yarn 12, e.g.cotton, and a UV-A transmissive synthetic yarn 14, e.g. yarns asdescribed under example 2. The fabric has regular, polygonal or almostcircular mesh openings 16 with a size W in the range from 100 to 300 μm,preferably about 200 μm. As can be seen in FIG. 1, the relatively largemesh openings formed by the regular yarn 12 are partly closed or reducedin size by the synthetic yarn 14 which is effective as a UV-B filter.

FIG. 2

The fabric 10 is manufactured in the form of a tube 10′ on a circularknitting machine 18 which has schematically been shown in FIG. 2. Theknitting machine has circular needle assemblies 28 with a diameter of76.2 cm and 11 needles/cm (28 needles/inch). In a specific example, thenatural yarn 12 is cotton 70/1 NM, and the synthetic yarn 14 ispolyester with 55 Dtex and 20 filaments (for example: type 55f20 t1001as mentioned under example 1).

FIG. 3

The manufacturing process for this example has diagramatically beenshown in FIG. 3. In step S1 the tube 10′ is knitted on the circulardouble knitting machine 18 with a double Jersey binding and with a yarntension of 0.03 N for polyester and 0.025 N for cotton. The yarn intakeis 24.6 cm/100 needles for polyester and 26.8 cm/100 needles for cotton.Thus, the resulting fabric will have a composition of 45% polyester and55% cotton, and the weight before dyeing will be 98.0 g/m².

In step S2, the tube 10′ is dyed in a bath process at a temperature of130° C. with disperse dyes for the polyester yarn yarn, after which itis cooled down to 95° C. and then the cotton yarn is dyed with directdyes. After dyeing, silicon based softeners will be added, the weight ofthe fabric will then be around 140.0 g/m².

In step S3, the wet, dyed fabric tube 10′ is cut and flat-dried. Then,the fabric is stretched and stabilised at a temperature of 190° C.

The final product is a double knitted pique-type fabric with a weight ofapproximately 130 g/m². The UV-A transmission is 44% and the UV-Btransmission is 12%. These figures may slightly change when the fabricis washed, but will remain at approximately 40% for UV-A and 10% forUV-B.

1. A fabric comprising: a first yarn having an ultraviolet radiationtransmission in the UV-A range of 320-400 nm of between 10 and 50% whilesubstantially blocking an ultraviolet radiation transmission in the UV-Brange of 290-320 nm, and at least a second yarn different from the firstyarn, the yarns being interweaved such that the fabric has regular meshopenings, and both the first yarn and the mesh openings together controltransmission of the fabric of between 20 and 65% for ultravioletradiation transmission in said UV-A range and between 3 and 20% forultraviolet radiation transmission in said UV-B range.
 2. A fabricaccording to claim 1, wherein the ultraviolet radiation transmission insaid UV-A range of the fabric is between 25 and 60% and the ultravioletradiation transmission in said UV-B range is between 5 and 15%.
 3. Afabric according to claim 2, wherein the ultraviolet radiationtransmission in said UV-A range of the fabric is between 30 and 45% andthe ultraviolet radiation transmission in said UV-B range is between 10and 12%.
 4. A fabric according to claim 1, wherein the second yarn is anon-elastic yarn.
 5. A fabric according to claim 4, wherein the firstand second yarn are interweaved via a double-knitting process.
 6. Afabric according to claim 4, wherein the content of the non-elastic yarnis between 15 and 85%, based on the total weight of the fabric.
 7. Afabric according to claim 4, wherein the weight of the fabric is between90 and 180 g/m².
 8. A fabric according to claim 3, wherein the secondyarn is an elastic yarn.
 9. A fabric according to claim 8, wherein thesecond yarn is a naked yarn, and the content of the second yarn isbetween 10 and 30% based on the total weight of the fabric.
 10. A fabricaccording to claim 9, wherein the fabric contains 30-50% of the firstyarn, and up to 60% of a third yarn, the third yarn being non-elastic.11. A fabric according to claim 8, wherein the second yarn is a corespunyarn.
 12. A fabric according to claim 11, wherein the fabric contains upto 30% of the second yarn based on the weight of the fabric.
 13. Afabric according to claim 12, wherein the fabric contains up to 10% ofthe second yarn.
 14. A method for manufacturing a fabric comprising thesteps of: taking a first yarn having an ultraviolet radiationtransmission in the UV-A range of 320-400 nm of between 10 and 50% whilesubstantially blocking an ultraviolet radiation transmission in the UV-Brange of 290-320 nm, taking at least a second yarn different from thefirst yarn, and interweaving the yarns such that the fabric is providedwith regular mesh openings and such that both the first yarn and themesh openings together control transmission of the fabric of between 20and 65% for ultraviolet radiation transmission in said UV-A range andbetween 3 and 20% for ultraviolet radiation transmission in said UV-Brange.
 15. A method according to claim 14, wherein the yarns areinterweaved via a knitting process.
 16. A garment made with a fabriccomprising: a first yarn having an ultraviolet radiation transmission inthe UV-A range of 320-400 nm of between 10 and 50% while substantiallyblocking an ultraviolet radiation transmission in the UV-B range of290-320 nm, and at least a second yarn different from the first yarn,the yarns being interweaved such that the fabric has regular meshopenings, and both the first yarn and the mesh openings together controltransmission of the fabric of between 20 and 65% for ultravioletradiation transmission in said UV-A range and between 3 and 20% forultraviolet radiation transmission in said UV-B range.
 17. A fabricaccording to claim 6, wherein the content of the non-elastic yarn isbetween 50 and 60%, based on the total weight of the fabric.
 18. Afabric according to claim 7, wherein the weight of the fabric is between125 and 150 g/m².
 19. A fabric according to claim 9, wherein the contentof the second yarn is around 20% based on the total weight of thefabric.